Effect of tunnel-spin polarization on spin accumulation in n-type Ge(001)/MgO/Co40Fe40B20

We found that a huge enhancement of electrical spin accumulation in n-type Ge(001) with the MgO/Co40Fe40B20 (CFB) spin-tunnel contact (STC) is realized by postannealing. The spin-resistance–area product (R s A) of this STC on n-type Ge after postannealing at 350 °C (1.97 × 106 Ωµm2) is nearly one order of magnitude larger than that of the as-deposited one (2.34 × 105 Ωµm2). The dependence of R s A on contact resistance, a scaling property, is also greatly modulated after postannealing. The epitaxial growth of CFB on an MgO(001) template and the consequent TSP improvement are responsible for such changes.